In recent years, with increasing demand for higher-performance electronic parts, miniaturization of semiconductor devices, speeding up of working speed, and densification of wiring have been in progress, and various forms of packages corresponding to them have been proposed. In semiconductor packages, adhesives are used for the purposes of stacking chips having through silicon vias in a three-dimensional structure, bonding a chip to a supporting substrate, and forming a package having such a hollow structure as that of an image sensor and MEMS. Adhesives used for these purposes require low stress, adhesiveness, insulation reliability, and reflow soldering resistance, and further require patternability, i.e., photosensitivity in order to simplify a process or to form a package with a particular structure.
As an adhesive satisfying so many properties, a polyimide-based adhesive with excellent heat resistance and insulation properties has been studied. In particular, as an adhesive having a photosensitive function, a technique for half-curing a polyimide precursor such as polyamic acid has been proposed in Patent Document 1, for example. In Patent Documents 2 and 3, a material comprising as a base resin a closed polyimide or the like for reducing thermal damage to surrounding components has been proposed. In Patent Document 4, a photosensitive adhesive composition mainly composed of an alkali-soluble polyimide resin that shows excellent low-temperature laminate properties after pattern formation has been proposed.